Trans fatty acids and cancers: AFSSA recommendations

The results of epidemiological studies were too few and inconsistent to enable a conclusion to be drawn as to whether dietary trans fatty acids (TFA) including conjugated linoleic acids (CLA) were beneficial or detrimental to the various sites of cancer studied. The effect of CLA isomers has only been studied in animal models, and mainly on mammary tumours. CLA - particularly the 9c,11t CLA - exerted an inhibitory effect on the initiation and development of these tumours, whereas a similar effect has not been observed in humans, whose intake level is much lower than the threshold required for an antitumour effect to be detectable in rodents. The aforementioned effect has been obtained in animal models at prolonged and high intakes, from 0.5 to 2% of the total energy intake, which corresponds approximately to 5-10 g/day in humans. The underlying mechanisms have not been identified and are probably indirect and multiple.